Clothing and associated wearing apparel for the body's extremities, such as gloves, hats, and socks, come under many constraints in their design, construction and use. Many end uses place unique requirements on the material utilized. Frequently, the material required does not exist, and as such there is an ever ongoing effort to develop new materials to meet these new, and/or more difficult requirements. To illustrate this situation, a particular problem which has confronted those in the art is the provision of a functional glove, with comfort, for clean room environments.
In the electronics and pharmaceutical industries requirements for contamination control in clean room environments have become more and more demanding. Contamination can result from air-borne particles of submicron size or from material transfer from one surface to another. One source of contamination is from the clean room personnel and their associated clothing. Therefore, on-going efforts exist in developing clothing articles, including gloves, that enhance contamination control. Contamination control is provided by a glove when:
1) The glove prevents particles, or other undesired materials from the hand, to pass from the hand to the outside of the glove. PA1 2) The glove can be rendered free of contamination before use by the wearer. PA1 3) The glove does not, during use, abrade or otherwise break down, and subsequently become a source of contamination. PA1 1) Form-fitting--A glove should be form-fitting, and contoured to the shape of the hand, neither having an undesirable excess and/or a bunching of the material, nor intense tightening upon the hand. PA1 2) Touch--Touch is defined as the array of sensations arising from the pressure sensitivity of the skin. Therefore, desirably the glove should not impair touch or tactility (i.e. the sense of touch) while picking up and handling objects. PA1 3) Dexterity--Dexterity is the skill in using one's hands. A clean room glove desirably, therefore, allows for great dexterity. PA1 4) Comfort--The glove should be comfortable during use, it is undesirable to have either an accumulation of sweat inside the glove or have the hand in intimate contact with something that feels "plastic or rubbery". PA1 1) provides contamination control, while being both PA1 2) functional (i.e.--form-fitting, with good touch and dexterity characterisitcs), and PA1 3) comfortable. PA1 (i) a microporous polymeric membrane PA1 (ii) a water vapor-permeable polymer and PA1 (iii) an elastomeric thermoplastic fibrous nonwoven web in which the fibers are elastomeric and are less than 50 micron in diameter, PA1 said polymer (ii) being continuous and being in contact with membrane (i) and substrate (iii), PA1 said composite fabric exhibiting an elastic modulus in at least one direction being less than about 15 pli, and said fabric having an overall thickness less than about 15 mils, and having a force to flex of less than 35 gm. in any direction PA1 said composite fabric being liquid water-impermeable and being water vapor-permeable to the extent of having a water vapor transmission rate of at least 5000 gm.m.sup.2 /24 hrs.
Workers in the clean room perform numerous operations while wearing gloves. Throughout the day, they must be able to perform these operations reliably and with minimum hinderance by their gloves. They must be able to handle objects, and move their hands and fingers, both freely and delicately. Therefore, desirable glove characteristics, from the wearer's consideration are:
Thus taken collectively, the desired clean room glove:
Currently, numerous different glove technologies are found for use in clean room gloves, however, no one technology exhibits all of the desired characteristics recited above.
Elastomeric resin gloves and their functionally beneficial characteristics have been taught in the art for some time. For instance, U.S. Pat. No. 3,094,704 to Abildgaard, teaches the control of thickness and resilience or elastomeric memory of the material used. Commercially, elastomeric resin gloves, such as those referred to as "latex gloves", are used in clean rooms. These gloves exhibit good functional characteristics and initial contamination control. They are, however, deficient in comfort characteristics. The sweat accumulation during use and the intimate film contact against the skin make them uncomfortable and thus undesirable for the wearer. Furthermore, in use these gloves shed submicron particles from the material surface and thus are a source of contamination.
Plastic and plasticized polymeric material, such as polyvinyl chloride ("vinyl") gloves, are also commonly used in clean rooms. Vinyl gloves suffer from the same comfort limitation found with latex gloves. Furthermore, due to their limited elastomeric characteristics, vinyl gloves must be oversized to fit on the wearer's hands. This oversizing not only is dificient in fit but compromises touch as well. Oversizing the glove also makes closure around the wrist more difficult in practice, thereby, increasing the risk of contamination. These gloves too, are known to shed submicron particles from the material surface and thus are a primary source of contamination.
As an improvement over the above, U.S. Pat. No. 4,670,330 to Seihi, provides for gloves consisting of a thin elastic film of hydrophilic polyurethane resin. Due to their moisture permeability, they exhibit less accumulation of sweat in the glove and are, therefore, more comfortable to the wearer. The hydrophilicity, and in turn, the moisture permeability, of this glove is limited in practice in that with increasing hydrophilicity the film swells excessively with water causing it to become unacceptably weak and eliminating any previous fit. Practically, this limits the comfort range of this glove. U.S. Pat. No. 4,783,857 to Suzuki, is directed to improving upon this via a prescribed polyoxyethylene content incorporated into the polyether segment of their polyurethane. Here again, the compromise between comfort and satisfactory glove physical properties is seen. In addition, both of these technologies do not overcome the undesirable feature of the hand in intimate contact with the film producing an uncomfortable feeling to the wearer. Furthermore, at least in the commercial gloves available according to the teachings of Seihi, the high modulus of elasticity of the material requires that the gloves be formed in a size larger than the hand. As such the gloves do not fit well on wearing, with concomitant loss of touch and more difficult wrist closure.
Fibrous sheet materials such as woven fabrics, knitted goods, nonwoven fabrics and the like, provide suitable comfort to the wearer but find limited use in contamination control. Particles of a submicron size, and oils from the hand, find pathways through the material.
An improvement on the sewn construction of most fibrous material gloves is seen in U.S. Pat. No. 4,660,228 to Ogawa, where a polyurethane nonwoven is heat sealed to form the glove. While this glove has superior fit to many sewn gloves it still suffers by having ready pathways for migration of contaminants.
Liquid watertight, but water vapor-permeable, membrane material exists which has been used increasingly in recent years for the production of articles of clothing. In practice, these membranes are most frequently in laminate form. Due to their water vapor-permeability they result in pleasant wearing properties. Suitable membrane material is made, for example, of expanded microporous polytetrafluoroethylene (PTFE), or even of a layered membrane of hydrophilic polyurethane imbibed into the surface of hydrophobic expanded microporous PTFE as taught in U.S. Pat. No. 4,194,041. Expanded PTFE membrane material has also been used for producing articles of clothing for use in contamination control intended for application in the clean room environment.
Glove insert technology of liquid watertight but water vapor-permeable material is known. Glove inserts are placed between an outer layer and a liner layer of the final glove construction. Inserts appear in the marketplace as heat bonded sheets of various materials such as hydrophilic polyurethane, expanded PTFE membrane, microporous polyurethane, or of copolyether ester film laminated to a knit (U.S. Pat. No. 4,493,870 to Vrouenraets). These inserts suffer from being over sized and as such do not fit the hand well in wearing. This results in loss of touch and dexterity.
Elastomeric composite fabrics of various descriptions exist in the art. A liquid waterproof, water vapor permeable elastomeric fabric is taught in the teachings of U.S. Pat. No. 4,453,511 to Worden. Specifically a membrane of continuous hydrophilic polyurethane and hydrophobic microporous expanded PTFE is laminated to a knit containing a spandex fiber. Clean room gloves of laminate of similar material have also been available commercially, in which the PTFE surface is oriented outward. The seams are sealed with a tape to eliminate the needle holes being a pathway for contamination migration. As seen in Comparative Example 1 hereinbelow, these gloves suffer functionally from a loss of touch and dexterity, due to the laminate thickness and seam construction.
Elastomeric composite fabrics comprising at least one layer of elastomeric nonwoven fabric are known. Typical of the composite elastomeric fabrics are those taught in U.S. Pat. No. 4,692,368 to Taylor, U.S. Pat. No. 4,657,802 to Morman and U.S. Pat. No. 4,655,760 to Morman. It should be noted that all of these elastomeric composite fabrics result in increased bulk over the base elastomeric nonwoven employed. Frequently this comes about by the "gathered" or "wrinkled" non-elastomeric material which puckers between sites bonded to the elastomeric nonwoven. Additionally, these materials suffer the same limitations cited above for fibrous materials employed in a glove configuration.
Elastomeric composite fabrics of elastomeric films on elastomeric nonwovens are known in the art and taught for instance in U.S. Pat. No. 4,660,228 to Ogawa, wherein an elastomeric polyurethane nonwoven taught specifically therein is combined with the modified polyurethane film according to the teachings of U.S. Pat. No. 4,539,255 to Sato. This technology represents an improvement over the gloves of hydrophilic resin alone, but suffers from the same compromise of water vapor permeability (and thus comfort) with satisfactory physical properties.
Unfortunately, the known elastomeric composite fabrics of the art have been lacking in one or more of the characteristics cited above as necessary for a satisfactory clean room glove material.